1. Technical Field
This invention relates to loudspeaker waveguides having internal plates that alter sound path lengths of acoustic elements.
2. Related Art
An individual loudspeaker typically has a driver unit connected to an outwardly expanding horn. In many loudspeakers, sound waves uniformly travel from the driver unit as a point source through the horn and outward in all directions. The resulting sound wave shape, usually known as spherical sound radiation, is similar to the ice-cream cone (hemisphere topped cone) shape of light traveling from a flashlight. However, a loudspeaker that directs sound waves uniformly in all directions generally is efficient only if listeners are located in each direction that the sound travels. Listeners in large-scale indoor and outdoor arenas typically are located only in a restricted listening area. For these arenas and in other applications, that portion of the acoustical power utilized to radiate sound waves upward above the loudspeaker largely is wasted.
In contrast to spherical sound radiation, cylindrical sound radiation essentially expands horizontally without expanding upward. The horizontal expansion of cylindrical sound radiation reaches out towards an audience while minimizing upward sound travel. Thus, cylindrical sound radiation is more efficient than spherical sound radiation in many loudspeaker applications.
One technique that created cylindrical sound radiation from loudspeakers involved vertically stacking a group of loudspeaker drivers so close together that the combined output took on a coherent wave front characteristic. This technique effectively converted the sound waves from each point source at the driver units to a plane source just outside of the end of the horns. However, the utilization of so many drivers to create cylindrical sound radiation often makes this a costly technique. Therefore, there is a need for a loudspeaker system that inexpensively produces cylindrical sound radiation.